When a structure, such as a vessel, consisting of steel plates is to be dismantled, a so-called gas cutting method is conventionally used. In this method, oxygen is blown onto a steel plate heated to a high temperature by an oxygen-acetylene gas flame, so that the steel plate is burned and any product obtained by burning is blown off. However, with this gas cutting method, a structure, such as a tanker which may contain a flammable material can catch fire and cause a fire or explosion. Even if the structure does not contain a flammable material, it is dangerous to use a gas flame. When a steel plate is coated, the coating film can catch fire by the gas flame to spread the fire. Oxygen is consumed by burning of the coating film, thus decreasing the gas cutting efficiency. When a steel plate is rusted, the gas cutting efficiency is decreased as well.
In another conventional method, small holes are continuously formed in a steel plate to allow cutting of the steel plate. However, this requires a large amount of labor and is thus not efficient.